1. Field of the Invention
An aspect of the present invention relates to an organic light emitting diode display device (OLED display device) and a method of manufacturing the same and, more particularly, to an OLED display device having uniform electrical characteristics and a method of manufacturing the same.
2. Description of the Related Art
Nowadays, in order to overcome the shortcomings of conventional display devices such as cathode ray tubes (CRTs), much attention is given to flat panel display devices (FPDs), such as liquid crystal displays (LCDs), organic light emitting diode display devices (OLEDs), and plasma display panels (PDPs).
An FPD such as an OLED display device or LCD includes a thin film transistor (TFT), which is used as a switching device or a driving device, and a capacitor, which is connected to the TFT, stores an external signal, and applies the stored external signal in the next signal period.
FIGS. 1A through 1E are cross-sectional views illustrating a process of manufacturing a conventional OLED display device.
Referring to FIG. 1A, a buffer layer 110 is formed on a substrate 100, which is a plastic substrate or a glass substrate. An amorphous silicon (a-Si) layer (not shown) is formed on the buffer layer 110 and then patterned to form a semiconductor layer 120 and a first capacitor electrode 125 for a capacitor. Thereafter, an insulating layer 130 is formed on the substrate 100.
Referring to FIG. 1B, a photoresist pattern 140 is formed on a region of the insulating layer 130 corresponding to the semiconductor layer 120. An ion implantation process is performed using the photoresist pattern 140 as an ion implantation mask, thereby defining source and drain regions and a channel region in the semiconductor layer 120 and implanting impurity ions into the first capacitor electrode 125.
Referring to FIG. 1C, the insulating layer 130 is etched to form an insulating layer pattern on the channel region of the semiconductor layer 120. A crystallization inducing metal layer 150 is formed on the substrate 100 and then removed from a region except the semiconductor layer 120 and the first capacitor electrode 125.
Referring to FIG. 1D, a gate insulating layer 160 is formed on the substrate 100. The substrate 100 is annealed, so that the source and drain regions and the first capacitor electrode 125 are crystallized by a metal induced crystallization (MIC) process, while the channel region is crystallized by a metal induced lateral crystallization (MILC) process.
Referring to FIG. 1E, a gate electrode 170 is formed to correspond to the semiconductor layer 120, and a second capacitor electrode 175 for the capacitor is formed to correspond to the first capacitor electrode 125. Thereafter, an interlayer insulating layer 180 is formed on the substrate 100, and source and drain electrodes 191 and 192 are formed on the interlayer insulating layer 180 to complete a TFT and a capacitor. Although not shown in the drawings, a first electrode, an organic layer, and a second electrode are formed to complete a conventional OLED display device.
However, when the semiconductor layer is crystallized by both the MIC and MILC processes as described above, MILC crystallinities run into each other in the channel region, thus generating an MILC front that is uncrystallized in the channel region. As a result, the mobility of charges is lowered, thus deteriorating the characteristics of the OLED display device.